Networks consisting of modules capable of communicating with each other and/or with a central network unit are well known. Communication between the network modules may take place via cables, wireless (e.g. radio frequency) links, or both. The network modules may be computers or other devices and are, in general, capable of processing information and of transmitting and/or receiving information.
Increasingly, sensor networks are used for the surveillance of dams, dykes, buildings, bridges, ships and other structures, and for measuring properties of such structures. In sensor networks, the network modules contain sensors which produce measurement data. These data are transmitted via the network to a central network unit for processing or for further transmission to a remote processing unit.
For a network to be operational, it has to be started up: communication with the network modules must be established in accordance with a certain network protocol. At start-up, network modules are typically assigned communication channels and/or time slots, and the various network modules may be probed in a certain order. However, this start-up process may fail, as a result of which the network will not be able to function properly, or may not function at all.
After a start-up failure, a network may be restarted. However, the problem that caused the initial start-up to fail may still be present and cause the restart to fail too. As a result, the network may be restarted several times without success. The prior art fails to provide an adequate solution for this problem.
Japanese Patent Application JP 64-10366 (NEC) discloses a system for reconfiguring a network. The network configuration information is revised when network elements are added to or deleted from the network. Network revision information is stored in a revision history file. When restarting the network after an addition/revision request, revision information is read from the network revision history file to revise the network constitution information. Although this known system is useful when altering the configuration of a network, for example by adding or deleting network modules, it offers no solution for start-up problems. In this known system, start-up failures will not influence the contents of the revision history file and hence the network will attempt to restart in the same manner, unless an external revision request is received. However, these revision requests are unrelated to start-up failures and will therefore not solve any start-up problems.